A tsunami is a huge sea wave, or also known as a seismic sea-wave. They are very tall and height and have extreme power. A tsunami is formed when there is ground uplift and quickly following a drop. From this, the water column is pushed up above the average sea level. Volcanic tsunamis can result from violent  submarine explosions. They can also be caused by caldera collapses, tectonic movement from volcanic activity,  flank failure into a water source or pyroclastic flow discharge into the sea. As the wave is formed, it moves in a vertical direction and gains great speeds in deeper waters and can reach speeds as fast as 650 mph. In shallow water it can still be as fast as 200mph. They travel over the continental shelf and crash into the land. This power doesn’t decrease when they hit land though, there is an extreme amount of energy when the water travels back towards its source. Approximately 5 percent of tsunamis are formed from volcanoes and approximately  16.9 percent of volcanic fatalities occur from tsunamis. (Tanguy, J.C. 1998)

Image 1 - This image shows how the eruption of a volcano on a waters edge causes a tsunami to form.

The debris avalance crashes into the sea once it travels down the volcanoes side pushing the water up as they meet. (Springer,L. 2005.).